Field of the Invention
The invention relates generally to the field of semiconductor device manufacturing and, more particularly, to metal sulfide films and methods for forming sulfur-containing thin films, such as by atomic layer deposition (“ALD”) processes. For example, metal sulfide films such as MgS films may be formed by ALD processes and may serve as an interface layer between a substrate and a dielectric layer.
Description of the Related Art
In an effort to continue to enhance the performance of high-k metal gate technology, the semiconductor industry has shown interest in high-mobility substrate materials, such as germanium, which exhibits desirable hole mobility, and group III-V materials, which exhibit desirable electron mobility. Suitable group III-V materials include, for example, GaAs, InP, InGaAs, InAs, and GaSb. However, problems with these new channel materials can be present at the interface between the high-mobility material and the overlying dielectric layer.
The high-mobility semiconducting channel, based on materials such as Ge and InGaAs, have a very high number of interface states. These states tend to pin the Fermi energy and can severely deteriorate the function of electronic devices. Sulfur passivation can be an efficient approach to minimize the interface states. Beyond passivating the surface, an interface layer is desirable for integration with a high-k dielectric layer. However, known interface layers have a variety of problems, such as not preventing oxidation of the underlying high-mobility channel and allowing for undesirable current leakage or charge trapping and not preventing up diffusion of group III-V elements or Ge into the gate dielectric.